Patent GB-680834-A (GB)
Title: Improvements in or relating to copying machine tools
IPC: B23Q35/18
Filed: 1950-04-17
Abstract: 680,834. Copy-milling. MARCHANT, L. E., FARR, C. P., and ROE (CANADA), Ltd., A. V. April 4, 1951 [April 17, 1950], No. 9347/50. Class 83 (iii). A machine-tool comprises a table 8a for carrying a number of workpieces and a pattern, a power-drive for reciprocating the table, a tracer 6 and a number of tools 4 mounted in a head 3, a power-drive to oscillate the head about an axis transverse to the direction of movement of the table, power means to drive a shaft 18 coaxial with the said axis to rotate the tools, and means responsive to the tracer to control one of said power drives. The head 3 is supported on trunnions 10, 11, the latter carrying a bearing for the shaft 18 which is driven by an electric motor. The table 8a carries a slide 8 on which fourteen turbine blade blanks are mounted, the slide 8 being inclined to assist the tracer in surmounting abrupt portions of the pattern. The head 3 is rocked by hydraulic pistons 24 while the table 8a is fed by a hydraulic piston 27 controlled by the tracer 5. A hydraulic motor 35 drives two pumps each having a small and a large volume unit. Valves 45, 46 operate to return the output of the large volume pumps to a reservoir 36 when a predetermined pressure is reached. The valve 45 supplies fluid through a reversing valve 47 having a controllable port 49 to regulate the feed rate of the piston 24. The valve 46 supplies fluid through a reversing valve 48 to the piston 27 and to an indexing piston 52. In operation, the table 8a is fed rapidly inwards until a dog 34 actuates a switch 33 to reverse the valve 48. One-way valves 50, 51, however, prevent a return stroke of the table and the build-up of pressure cuts out the large volume unit. The hydraulic tracer 6 thus assumes complete control of the table with the pressure supplied by the small volume unit. Actuation of the switch 33 also actuates the valve 47 to start a downward stroke of the head 3. At the end of the downward stroke an adjustable abutment 31 on a disc 32 actuates a switch 30 to cause a rapid return of the head. At the upper end of the arcuate movement of the head a second switch 30 is actuated to stop the head and initiate a further feed movement of the table 8. At the beginning of each feed movement of the table 8a the piston 52 is actuated to index the slide 8 transversely by, say, 0.01 inch. When the table has been indexed across the whole width of a work-piece, an adjustable dog 28 actuates a switch 29 to move a solenoid 54, Fig. 6. The solenoid causes reversal of the hydraulic feed valve controlled by the tracer 6 and the table is withdrawn. Further dogs 28 may actuate plungers 29 which are connected to limit switches coacting with further switches 30 to vary the lower limit of the arcuate movement of the head 3. In a modification, the circuit is arranged for cutting to take place on the upward swing of the head 3. In a further modification, the table 8a is actuated by a motor-driven feed-screw and the tool-head is actuated by an electric motor. The tracer is then of electrical type acting through an electronic circuit. In yet other modifications the table 8a is indexed and the slide 8 is reciprocated or a single table which is both indexed and reciprocated may be provided. The table instead of the tool may be controlled by the tracer. Beds and framing; cooling tools and work; electric heating.-The bed 1, Fig. 1, formed with two uprights 2 contains four compartments housing respectively the hydraulic pump unit 35, the hydraulic reservoir 36, a coolant reservoir and the electric motor. The coolant is passed through heat-exchange pipes 39, 40, the shaft 18 being the hottest part of the machine, whence it is passed to pipes 41, 42, to the tools and work and also to the table 8 which is thus heated to a temperature corresponding to that of the tool-head. Alternatively, thermostatically-controlled elements may be mounted in the table 8.